18Hz baby! Anyway I'm very happy with the way they turned out. 10" Vifa woofers from about 12 years ago in just the right cabinet is giving me some very detailed, clean, deep and tight bass. Not boomy home theater type bass. Very nice bass that blends well with the main speakers. Anyway I'm happy and want to share the results. If anyone wants to build their own or has questions, you can feel free to ask me. By the way,they are driven with a really cheap 125wpc amplifier by Nexxtech (also sold as Optimus, Pyle and Pyramid). Normally these brands are junk but surprisingly this amp had some good reviews online regarding its sound quality. Its really only 80wpc but bass is controlled and accurate. Cant ask more. Picked it up for $129 I have a dedicated electronic crossover at 47Hz.